Optical switches which afford an optical connection of a single input waveguide with a plurality of output waveguides are known in the art. Devices described in U.S. Pat. No. 4,896,935 and U.S. Pat. No. 4,834,488 to Lee operate by rotating the end portions of certain fibers to align them optically with other fibers, all the fibers (or at least their end portions to be aligned) being positioned in a common plane. U.S. Pat. No. 4,378,144 to Duck et at. proposes an arrangement wherein a faceplate comprising a number of collimating lenses along a pitch circle is attached directly to a stepping motor, the shaft of the motor being coaxial with the pitch circle. A rotatable arm with a collimating lens is attached to the shaft for rotation along the pitch circle, with a small distance therebetween, so that the lens of the arm can be optically connected with the lenses on the faceplate when the rotatable arm is moved by means of the shaft of the stepping motor. An optical input fiber is connected to the collimating lens of the arm and a plurality of optical output fibers is attached to the respective collimating lenses on the faceplate for a switching operation when the rotatable arm moves from one position to another.
While the device of Duck et at. is useful, it has certain disadvantages. Since the output fibers are arranged parallel to the axis of the stepping motor and surround the motor, and since the input fiber is rotated along the pitch circle for alignment with the output fibers, the pitch circle must have a diameter at least equal to the diameter of the stepping motor. This creates a demand for space as the face, plate has a larger diameter than the respective size of the stepping motor, and also increases the possibility of an alignment error because of a relatively large radius of the pitch circle.
An attempt to solve the above problems was made in U.S. Pat. No. 5,317,659 to Lee. The end portions of a number of optical fibers are fixed onto the conical surface of a supporting frame. The end portion of a movable fiber is rotated about the axis of a conical surface so that the end portion of the movable fiber is aligned with one of the fixed fibers.
While the device of U.S. Pat. No. 5,317,659 overcomes the problem of the size of the faceplate of Duck '144, the device itself is rather difficult to manufacture and may be prone to alignment problems.